NCERT MCQ Solutions for Class 10 Science Chapter 10 Human Eye and Colourful World

The iris is a pigmented muscular diaphragm that controls the size of the pupil. By contracting or relaxing, it adjusts how much light enters the eye ensuring proper vision in both bright and dim lighting conditions.

The convex lens in the human eye bends incoming light rays to form a small inverted real image on the retina which is later processed and corrected by the brain.

Accommodation is the eye’s ability to adjust the curvature and focal length of the lens using ciliary muscles so it can focus on both nearby and distant objects clearly.

Hypermetropia or farsightedness occurs when the eye focuses images behind the retina. This leads to difficulty in seeing nearby objects while distant vision remains relatively unaffected.

A concave lens diverges incoming light rays so that the image of a distant object is formed on the retina correcting the condition of nearsightedness or myopia.

Presbyopia is an age-related eye defect where the eye gradually loses the ability to focus on nearby objects due to reduced flexibility of the lens and weakening of ciliary muscles.

The least distance of distinct vision for a normal adult eye is about 25 cm. It is the minimum distance at which the eye can comfortably see objects without strain.

Twinkling occurs due to atmospheric refraction. Light from stars changes its path as it passes through varying air layers of different densities causing stars to appear as if they flicker.

Planets are closer to Earth and appear larger than stars. Their light passes through the atmosphere from a wider area which averages out atmospheric disturbances so they do not twinkle.

Violet light has the shortest wavelength among visible colors and refracts the most when passing through a prism due to its lower speed in the medium compared to other colors.

Dispersion happens because different colors of light travel at different speeds through glass. This causes each color to refract at a different angle splitting white light into a spectrum.

A cataract is a condition in which the lens of the eye becomes cloudy or opaque due to aging or damage reducing the ability to see clearly and sometimes leading to blindness.

The Tyndall effect occurs when light is scattered by small particles in a colloid or in very fine suspensions. It helps in visualizing the path of light in a mixture like mist.

The shorter wavelengths of blue light are scattered more than other colors by the gases and particles in Earth’s atmosphere which makes the sky appear blue during the day.

Red light has the longest wavelength so it scatters the least in the atmosphere. This makes it visible from long distances and ideal for warning signs and signals.

When all the dispersed components of white light are brought back together by using another prism or a lens they combine again to form white light as originally emitted.

The power of a lens indicates its ability to converge or diverge light and is measured in dioptres. It is the reciprocal of the focal length of the lens in meters.

Eye donation involves the transplant of the cornea from a donor to a recipient. It can restore vision in people suffering from corneal opacity or damage but not other eye conditions.

The angle of the prism is the angle formed between its two refracting surfaces. This angle influences the deviation of light rays as they pass through the prism.

In vacuum there are no particles to impede its motion so light travels at its maximum speed of approximately 3×10⁸ meters per second which is faster than in any medium.